1. Field of the Invention
The present invention relates to a performance regulating device for a fluid machinery, more particularly to a performance regulating device for a fluid machinery, which is suitably used for the pump for circulating cool or hot water.
2. Discussion of the Background
The method for controlling rotation speed of a motor pump through an inverter device (frequency converter) is well known in the art. This method can be very effective means for energy saving in the application of the pump for supplying water and so on in which a violent fluctuation of load is occurred, as well as in the application of the pump for circulating water.
A general purpose pump is not manufactured according to a specific standard specification, but is selected according to required specification. Namely, the general purpose pump is not order-made product which satisfy a specific specification (flow rate, pump head), but is selected from inventory for use so as to satisfy the scheduled specification. Additionally, the scheduled specification is generally calculated so as to satisfy a maximum flow rate in view of enough margin of expected flow rate. The head loss of the piping will be determined in view of enough margin and aged deterioration. Accordingly, when the pump is operated actually, the valves are controlled for suppressing the over flow rate, thus resulting to a waste of the energy. Even if the pump is selected in accordance with a calculation with calculating formulae, more or less waste of energy will be occurred.
In order to save energy, it is necessary to operate the pump in accordance with the xe2x80x9ctruexe2x80x9d specification, thus realizing effective operation of the pump without energy loss. The xe2x80x9ctruexe2x80x9d specification is only acquired after actual operation of the pump is carried out on the site, where actually required lowest flow rate and pump head can be found merely by operating the pump.
When it is found by the operation of the pump on the site that the capacity of the pump is too large, the energy can be saved by the following countermeasures:
(1) exchanging the pump with a pump of one rank reduced capacity; and
(2) reducing the outer diameter of the impeller to reduce the performance of the pump to the suitable value.
However, these countermeasures require additional cost, and it is difficult to retrieve the performance of the pump of thus reduced performance. On the contrary, the inverter device can control the performance of the pump easily and retrievably, so that the pump can be operated to save energy in accordance with the situation of the site without requiring above mentioned countermeasures.
In a case of incorporating an inverter device into an existing pump on a site, the energy can be saved by the following manners, which has advantages and disadvantages as follows:
(1) A Method for Controlling the Existing Motor Pump by Additionally Installed Inverter
(Advantage)
It is unnecessary to alter the motor pump itself.
(Disadvantage)
Generally, the circumstances in which the pump is installed are humid and unsuitable for additionally installing the inverter device. In this view point, it is preferable to incorporate the inverter device into the control console for controlling the motor pump. It is thus necessary to modify the existing control console or to construct new control console for incorporating the inverter device.
(2) A Method for Exchanging the Existing Motor Pump with a Motor Pump Incorporating an Inverter Device
(Advantage)
Any modification of the control console is substantially unnecessary.
(Disadvantage)
In this method, it is necessary to exchange the motor pump wholly. The exchanging of the existing pump before reaching the end of its service life is disadvantageous in respect of the cost.
(3) A Method for Exchanging the Motor Portion of the Existing Pump with a Motor Incorporating an Inverter Device
(Advantage)
Only exchanging the motor portion is required. However, disassembling operation and reassembling operation of the pump portion is also required except for a pump of directly coupling type. It is substantially unnecessary to modify the control console.
(Disadvantage)
Exchanging of the existing motor before the limit of its service life is disadvantageous in respect of the cost.
In view of the above mentioned problems, the present invention provides a technology that performance regulating of pump is easily carried out, and the energy to be consumed thereby is reduced. Namely, it is an object of the present invention to provide a performance regulating device for fluid machinery that without requiring any modification or change of existing pumps or existing control consoles, merely adding an inverter device can enable performance regulating of the pumps so as to save energy.
To achieve above object, according to an aspect of the present invention, there is provided.
In accordance with the present invention, the frequency converter is sealed completely against the atmosphere, so that the humidity around the pump and the rain do not affect the frequency converter. Further, the degradation of the insulation resistance due to the condensation of water within the casing can be avoided, even if the water cooling structure as mentioned below is adopted.
The submerged cable may be used as input means and output means. In such cable, the clearance between the core and the insulation is sealed hermetically, and the clearance between the insulation and the covering is also sealed hermetically.
The present invention is most effective when the fluid machinery is a motor pump of turbo type. The condensation of water can be avoided when the frequency converter is cooled by liquid to be handled by the pump. The condensation of water may be occurred with the casing due to cooling by the circulation of the cooled water especially in summer season. Further, an air cooling fan used in the general purpose inverter device is not required.
According to an aspect of the present invention, heat radiating means is provided for transferring a heat generated by the frequency converter to a pipe to be connected to the pump through the surface of the pipe. Thus the heat generated by the frequency converter can be radiated to the fluid, which is handled by the pump.
According to an aspect of the present invention, heat radiating means is provided on the casing, and a flow passage is provided through the heat radiating means for passing a fluid to be handled by the pump. At a result, the heat generated by the frequency converter is radiated effectively by the fluid, which is handled by the pump.
According to an aspect of the present invention, heat radiating means is provided on a casing, and a flow passage is provided through said heat radiating means for passing a fluid, which is handled by the pump. Here, heat radiating means is a water cooling heat sink of stainless steel to which the liquid to be handled by the pump is introduced through a bypass pipe (tube).
According to an aspect of the present invention, a heat radiating plate of air cooling type is provided on the casing of the frequency converter. The heat radiating means can be formed by the coupling guard made of aluminium alloy. Air stream generated by the rotation of the coupling is directed to flow against the coupling guard to cool it. The coupling guard is provided with a plurality of air cooling fins.
According to an aspect of the present invention, a switch is provided by which the output frequency can be varied in stepwise manner, for example in 8 steps by 5% each. At a result, the switch allows the user to regulate the performance of the fluid machinery easily. The switch is not a volume control dial of analogue type, so that the switching between steps can reliably be effected. When the volume control dial is employed, means for displaying the output frequency, for example, a liquid crystal monitor is required. Namely, control operation of the volume control dial does not show real operational condition of the pump, for example, rotational speed of the pump. On the other hand, the stepwise switch select one of the positions hereof corresponding to the preliminary certified operational condition, so that the performance of the pump can be regulated reliably, easily, and reproducibly.
According to an aspect of the present invention, the casing for housing the frequency converter is commonly used with a frequency converter assembly to be mounted on the outer surface of the pump and cooled by water. At a result, a pump with inverter device can be delivered to the application of newly constructed pumping facility. With respect to the existing pumping facility before limit of its service life, the performance regulating device as an flow rate control means can be supplied to the market with high productivity and low cost.
According to an aspect of the present invention, the performance regulating device is constructed that the frequency converter begins to output electrical power automatically when electric power is supplied thereto. This means that the fluid machinery can be started merely by making the power switch xe2x80x9conxe2x80x9d on the control console, so that the performance regulating device can be mounted anywhere, when the device is mounted on a pipe. For example, the regulating device can be mounted with taking the children""s play into consideration, or can be mounted at a narrow limited space.
The present invention can be utilized not only as a performance regulating device for a fluid machinery, but also as a frequency converter for controlling the rotational speed of general machine including a motor. Further, the device of the present invention can effectively be used in the out door condition of under rain weather since the casing is sealed hermetically.
The frequency converter of the present invention does not require an air cooling fan, which is used in the general purpose inverter. Thus, malfunction of the fan can be avoided, and stop of cooling is prevented.
In the second embodiment of the present invention, there is provided a performance regulating device for a fluid machinery comprising a frequency converter, typically an inverter device, a casing for housing the frequency converter, input means and output means connected to the casing, and an output frequency regulating device, wherein the casing of the performance regulating device for the fluid machinery is of weather proof structure avoiding the ingress of the rain water into the casing.
The inverter devices of relatively small output are often of air cooling without blower type. These inverter devices does not require the water cooled structure, so that no countermeasures against the condensation of water is required. However, the pumping facility are often provided on the out door condition, so that it is desirable to make the inverter devices to have weather proofness.